The invention relates to a device for driving a weaving frame in a weaving machine, comprising a drive with a motor or a geared motor, provided with a bearing on its output shaft, with an eccentric shaft and with a driving rod. On the other hand, the invention relates to a weaving machine provided with one or several such devices.
When weaving, warp yarns are positioned with respect to weft insertion means in order to realize the shed required to manufacture a specific fabric. Once the warp yarns have taken up their exact positions when forming the shed, the one or several weft insertion means will insert the necessary wefts through the shed which, in turn, will be pushed against the fell of the fabric by the weaving reed. Then the warp yarns will be brought into a next position in order to form the next shed, before inserting one or several new wefts.
As for most fabrics, quite a few warp yarns, have to be brought into the same position across the width of a weaving machine with respect to the weft insertion means, the heddles, through which these warp yarns are extending, are hung in a weaving frame which is driven in order to take up these positions. This applies both to flat fabrics where usually all the warp yarns are involved and to weaving pile fabrics where likewise all the warp yarns can be involved, but where things are usually limited to the backing warp yarns. Driving the weaving frames occurs in such a manner that, after weft insertion, each weaving frame takes up a position with respect to the weft insertion means, such that the warp yarns are forming the new shed required and a new weft may be inserted.
A great number of weave structures are characterized by a positioning pattern of the warp yarns with respect to the weft insertion means which is repeating itself over a limited number of wefts, for instance 2, 4, 6 or 8 shots. The weaving frames being driven here by a cam mechanism, the cam realizing the successive positions of a weaving frame in accordance with one or several positioning patterns which are repeating. By making use of different cams for the different weaving frames or at least positioning the cams for driving the different weaving frames in a different manner with respect to one another, the different weaving frames are taking up different positions in order to form the shed required each time to realize the fabric desired.
In order to drive the weaving frames with a more random positioning pattern, an electronic dobby device may be used. With such a device the dobby device will be able to select any position when forming the shed for any selection, in a manner independent of the preceding one and will also be possible to manufacture fabrics without the repeat pattern mentioned in the positions of the warp yarns.
A further, even more flexible method for driving weaving frames consists in providing each weaving frame with its own separate motor in order to bring the weaving frame, each time, in the position required. This method not only enables a random shed forming pattern to be realized, as when using dobby devices. By driving the motors separately it is also possible to impose a particular trajectory as a function of the time, on each motion of each weaving frame, also during its moving from one position into another. This, among other things, will prevent all the warp yarns of each combination of two weaving frames from crossing at the same moment. For it will be possible to ensure that the warp yarns of two weaving frames will get crossed at some other time than a combination of warp yarns of two other weaving frames will get crossed. Furthermore, in this manner, it will also be possible to open the shed more rapidly or more slowly in order to allow the weft insertion more time or less time per machine cycle, for instance, as a function of the fabric, the weaving speed, the width of the fabric or as a function of the weft yarn. It will also be possible to adjust the trajectory of the weaving frame, by means of certain types of these drives equipped with separate drive motors, or to bring the weaving frames into such a position, that the yarns will be subject to a reduced stress when the machine is stationary.
In the European patent application 1 215 317 a motor arrangement for such a device is described, in which it is made possible to install a considerable number of motors in order to drive a considerable number of weaving frames, each motor output shaft being linked to an eccentric shaft, to which a driving rod is linked, which is connected to a weaving frame by means of levers and rods. The continuously rotating eccentric shaft imposes a rocking motion on the driving rod, which is converted into an up and down movement of the weaving frame by linking the driving rod to the other levers and rods. This arrangement requires motors having a high torque and a quick reaction time, which will render this motors very expensive. Furthermore, the driving rod is no longer supported by bearings outside the motor, so that the reactive forces caused by the tension of the warp yarns on the weaving frame which are transmitted to the eccentric shaft through the connecting bars and levers and the driving rod will end up completely, as a load on the bearings of the drive motor. Because of this, the bearings in the motor on the side of the output shaft will be subjected to an additional heavy load, which may cause them to wear out rapidly and to be of a short operating lifetime.
In the European patent application EP 1 477 598 a solution to this problem is described, in which the installation of cheaper motors mounted on one or several frames of the shed forming device is used, each motor being linked to a reductor on the output shaft, which, in turn, is attached to a frame of a shed forming device and the eccentric output shaft being supported by additional bearings in the frame of the shed forming device on the side away from the motor and the reductor. In this manner, the forces in the bearings are reduced and the load imposed on the motor is likewise reduced, as the motor may be operating at a higher speed and may supply a lower torque, which will be converted by the speed reductor into a lower speed and a higher torque. This will render the device significantly cheaper.
In the European patent application 1 489 208 a device is likewise presented equipped with a geared motor, the motor performing an oscillating motion. It is no longer necessary, that the output shaft on which the driving rod is mounted will be an eccentric shaft. The geared motor also is attached to a frame, the output shaft extending through the frame, where it may be connected to a driving rod. The load, which because of the tension of the warp yarns, is guided to the bearing on this output shaft, through the heddles, the weaving frame, the levers and the driving rods, is a very heavy one for this bearing, as the output shaft is supported by a one-sided bearing only.
For a strong solution concerning motor driven weaving frames at a favorable cost and presenting a long operating lifetime it is important that the output shaft of the motor or the reductor (if installed) is supported by a double-sided bearing arrangement. This will strongly reduce the forces acting on the bearings and will also reduce the deflexion of the output shaft, giving cause to a greater strength and less vibrations. These advantages last-mentioned will become more important the more the two bearings are situated closely one to another.
The solution as proposed in EP 1 477 598 has a double-sided bearing arrangement on the output shaft, but has the disadvantage that attaching the geared motor to the frame of the shed forming device on the one hand, and the bearing arrangement of the eccentric shaft on the other hand, will make high demands on the precision of the frame and the geared motor. Finally, the bearing seat in the frame for the abutment has to be positioned accurately with respect to the bearing seat on the output shaft of the geared motor. For this purpose, the position of the bearing seat in the frame has to be provided very accurately with respect to the fastening elements of the frame where the geared motor has to be attached to the frame on the one hand. On the other hand, the fastening elements of the geared motor to be attached to the frame should be carried out very accurately with respect to the bearing in the geared motor. Finally, the connection between the geared motor and the frame has to be carried out with great precision, for instance, by using dowel pins, so that the precision of the various components should not be counteracted by an inaccurate connection. All this will increase the cost of both frame and geared motor, as well as the installation costs to connect the geared motors to the frame. Furthermore, the fact remains that the bearing seat in the frame is meant to fit a bearing of certain dimensions. When, because of different loads exerted on different weaving frames, the decision should be made to use different geared motors and eccentric shafts with different bearings, such a frame will not allow for weaving frames having different bearings on the eccentric to change positions in their drives.
In case the geared motors are installed on both sides of the frame of the shed forming device, as represented in the FIGS. 1, 2, and 5 of EP 1 477 598, the bearing seats in the frame for the bearings on the eccentric shafts, have to be finished centrally in the frame, which is a complicated and expensive operation. Moreover, both the connection of the eccentric shafts on the output shaft of the geared motor and the bearing arrangement of the eccentric shafts in the frame will require space inside the frame, which will prevent the frame from being made more compact or from driving more weaving frames with the same dimension of the frame. In the embodiments represented in the FIGS. 5, 6, 7 and 10 of EP 1 477 598 the eccentric shafts are of unequal length, which will have a different influence on the behavior of the different weaving frames when operating.